Hollow microgels reveal promising properties for applications as novel carrier systems. The combination of two spatially separated polymeric shells with distinct volume phase transition temperatures (VPTTs) in water lead to an advanced responsiveness which enables the separate control of the interactions between both the microgel and its surrounding and the microgel and possible guest species inside the cavity. This makes these microgels highly interesting as potential thermoresponsive nanocapsules.<br/><br/>Here, doubly thermoresponsive microgels with an inner poly(N-isopropylmethacrylamide) shell and an outer poly(N-isopropylacrylamide) shell are studied in presence and absence of a stiff silica core. Above, below and between the distinct VPTTs of the two polymers, small-angle neutron scattering with contrast variation reveals different responses of the core-double-shell and the corresponding hollow microgels. The former show a strong interpenetration of the polymeric shells when the outer network is collapsed while the inner shell is already swollen. We observe an increase of the polymeric volume fraction above the volume fraction of the microgel in the complete deswollen state. As predicted by our computer simulations, an appropriate choice of cross-linking density, leads to the generation of pitted double-shell nanocapsules which maintain an inner cavity independently on the swelling state of the shells (see figure).

Interplay of spatially separated polymeric shells in doubly thermoresponsive microgels in presence and absence of an incompressible core

255th National Meeting (2018)

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